How Does Rain Affect Chemicals and PH in a Swimming Pool

Does rainfall change the water chemistry?

Yes, it does but keep in mind that minor amounts of rain aren't going to change the chemistry much. Rain is acidic. It has a lower pH level than what we keep our pool at. We wanted to keep the pH in our pool around 7.6. The reason for this is that the human eye has a pH of 7.5. Major fluctuations from this can cause serious discomfort. You may have heard many times of people complaining that "My eyes are burning, the chlorine is too high" Very rarely is chlorine an issue if your eyes are in discomfort while swimming. It is most likely that the pH is low, or acidic. Normal rainwater has a pH of around 5.0. So depending on how much rainfall, it can lower the pH of the pool.

Do i need to raise the Ph every time it rains?

Not necessarily. It depends on the amount of rain and also the current water chemistry. If you have a light rainfall, it may temporarily lower the pH in the pool, but not by much and will come back up on its own. If you always maintain proper water chemistry, especially pH and Alkalinity, a bit of rain in the pool is nothing to worry about. A large amount of rain however, such as a strong thunderstorm or a rain over 2-3in a short amount of time will more than likely require a pH adjustment.

Are there benefits to rain in the pool?

Yes, rain can be beneficial to pool water in certain instances. There are certain chemicals in pool water that the levels can not be lowered without diluting the water. These are stablizier and calcium. Basically if you use chlorine tablets, they have stabilizer in them and over time, can over stabilize the pool water and will to be diluted. Also calcium levels that are high, rainfall can be a benefit to diluting the water as well. If you keep your water balanced on a professional level, the pool will not turn green after a rainfall. Accuracy is important in maintaining a good chemical balance.